Control methods for the synchronization and phase shift of the pulse width modulation (PWM) strategy of power converters
First Claim
1. A method of controlling a plurality of power converters that can be used to interface to an ac supply network, each power converter comprising a network bridge having ac terminals connected to the ac supply network, the network bridge operating in accordance with a pulse width modulation (PWM) strategy represented by a carrier waveform having the same switching period and which causes at least one unwanted harmonic in the supply network voltage, the method comprising the steps of:
- generating, by a first power converter, a time signal to act as a time datum;
transmitting, by the first power converter, the time signal to at least a second power converter; and
providing the switching period of the PWM strategy of each network bridge with a different time offset relative to the time signal to provide a different phase shift in the carrier waveform such that the at least one unwanted harmonic in the supply network voltage is at least partially cancelled.
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Abstract
A method of controlling a plurality of power converters 1a, 1b and 1c can be used to interface to a supply network, ac busbar etc. Each power converter includes a network bridge 14 operating in accordance with a pulse width modulation (PWM) strategy having the same switching period and which causes at least one unwanted harmonic in the supply network voltage. The method includes the step of providing the switching period of the PWM strategy of each network bridge with a different time offset relative to a time datum such that the at least one unwanted harmonic in the supply network voltage is at least partially cancelled. Two alternative ways of providing the time offset are described.
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Citations
39 Claims
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1. A method of controlling a plurality of power converters that can be used to interface to an ac supply network, each power converter comprising a network bridge having ac terminals connected to the ac supply network, the network bridge operating in accordance with a pulse width modulation (PWM) strategy represented by a carrier waveform having the same switching period and which causes at least one unwanted harmonic in the supply network voltage, the method comprising the steps of:
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generating, by a first power converter, a time signal to act as a time datum; transmitting, by the first power converter, the time signal to at least a second power converter; and providing the switching period of the PWM strategy of each network bridge with a different time offset relative to the time signal to provide a different phase shift in the carrier waveform such that the at least one unwanted harmonic in the supply network voltage is at least partially cancelled. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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- 19. A plurality of power converters that can be used to interface to an ac supply network, each power converter comprising a network bridge having ac terminals connected to the ac supply network, the network bridge operating in accordance with a pulse width modulation (PWM) strategy represented by a carrier waveform having the same switching period and which causes at least one unwanted harmonic in the supply network voltage and a controller, wherein a time signal that acts as a time datum is generated by a first power converter and is transmitted to at least a second power converter, and wherein the controllers of the plurality of power converters are arranged to provide the switching period of the PWM strategy of each network bridge with a different time offset relative to the time signal to provide a different phase shift in the carrier waveform such that the at least one unwanted harmonic in the supply network voltage is at least partially cancelled.
Specification